The invention relates to a method for treating a carbon dioxide-containing waste gas from an electric smelting process.
During operation of a conventional electric arc furnace (EAF) hot waste gases escape with a temperature of more than 1000° C. To remove pollutants and residues from combustible components the gas is initially subjected to re-combustion. Subsequently the waste gas is mixed with air, known as factory air, from the surroundings of the furnace, which has a very high proportion of dust. All the dust is removed from the waste gas by an electrostatic dust separator or by a bag filter system. For this purpose the waste gas must be cooled to a temperature of less than 180° before filtering.
With a shaft electric arc furnace the enthalpy of the furnace waste gas is used for scrap preheating. This results in increased concentrations of pollutants (e.g. VOC, dioxins, furans or the like) so that re-combustion is necessary to destroy these pollutants. Subsequently the waste gases must be rapidly cooled (quenched) to avoid renewed formation of the pollutants. Dust removal, as described above, is carried out thereafter. In accordance with the related art the heat is removed from the waste gas by water cooling and/or mixing the gas with cold, dust-laden factory air and no further use is made of it. The waste heat is removed by cooling and not used for other processes. A heat exchanger may possibly be employed in a few plants to incorporate the waste gas for generation of steam. In particular the carbon dioxide contained in the waste gases is not converted, but is discharged in the chimney into the environment.
JP 2010 223573 A discloses a method for treatment of a waste gas from iron or steel production, e.g. from electric arc furnaces. The carbon dioxide-containing gas is reformed by an endothermic reaction with a hydrocarbon-containing gas, e.g. methane into carbon monoxide and hydrogen. The resulting gas is then used as a combustion gas.
Furthermore U.S. Pat. No. 3,976,427 A discloses a method for metal production in an electric furnace. The carbon dioxide-containing waste gas is cooled by a reaction, with water and/or hydrocarbons for example with the formation of carbon monoxide and hydrogen.